As background techniques for the present invention, members with a film formed to contain Sn as its main constituent, methods for forming films, and soldering methods are disclosed in, for example, International Publication WO 2006/134665 (see Patent Document 1).
In recent years, from an environmental perspective, the film formation by metal plating containing Sn as its main constituent without containing any Pb on terminals for connectors, lead frames for semiconductor integrated circuits, etc. has been examined, in place of conventionally applied Sn—Pb solder plating. Such films containing no Pb are likely to generate Sn whisker-like crystals referred to as whiskers. The whiskers range from several μm to several tens of mm in length, and may cause failure of electrical short circuit between adjacent electrodes. In addition, when the whiskers are detached from the films to fly apart, the flying whiskers will cause short circuit inside and outside the system.
The technique disclosed in Patent Document 1 forms alloy grains of Sn and Ni at Sn crystal grain boundaries, in particular, in films containing Sn as their main constituent, for the purpose of providing members including films that can inhibit the generation of such whiskers. The formation of such Sn—Ni alloy grains can inhibit whisker growth.    Patent Document 1: International publication WO 2006/134665